Bottom-hole catalytic heater using heat transfer liquid



Dec. 14, 1965 E. B. HUNT 3,223,031

BOTTOM-HOLE CATALYTIC HEATER USING HEAT TRANSFER LIQUID Filed May 24, 1963 ELTON B. HUNT INVENTOR.

ATTORNEY.

United States Patent 3,223,081 BOTTOM-HOLE CATALYTIC HEATER USING HEAT TRANSFER LIQUID Elton B. Hunt, Tulsa, ()kla., assignor to Pan American Petroleum Corporation, Tulsa, Okla, a corporation of Delaware Filed May 24, 1963, Ser. No. 283,001 3 Claims. (Cl. 126-360) The present invention relates to a heating apparatus of novel design for use in oil wells. More particularly, it is concerned with a kind of bottom-hole heater capable of distributing heat to an oil-bearing formation rapidly and evenly.

Briefly, my invention is based on a means for distributing evenly the heat from a bottom-hole heater in which high temperatures are generated by contacting an airfuel mixture with an oxidizing catalyst. In accordance with the invention this is accomplished by jacketing such heater and completely or partially filling the jacketed space with a suitable heat-transfer material.

Many methods have been employed in the prior art for heating oil wells, e.g., by electrical means, by injecting heat transfer agents into the well such as steam, hot oil, etc., and by burning natural gas in the well bore. Considerable difiiculty has been encountered in the application of electric well heating owing to the highly corrosive nature of oil field brine, sulfur compounds, and other components of the fluids produced through the well bore. These fluids penetrate the innermost parts of the well heater, and even traces of moisture cause short-circuiting of the apparatus necessitating shutdown, removal and repair. These difliculties materially reduce the operating efficiency of such heating processes. Well bore liquids also penetrate and permeate the customary insulating materials rendering them practically useless. These problems are peculiar to the well heating art and are not generally encountered in other applications of electrical heating.

One of the principal drawbacks of the gas or liquid fueled heaters is that it is extremely difficult to avoid damage to the casing and any well equipment present in the area where heat is being applied. This is due to the fact that the temperature at which heaters of this kind operate cannot be maintained at levels which such equipment can withstand. One of the difliculties with electrical heaters is their tendency to short out owing to hot spots developing through poor heat exchange, generally resulting from coke formation on the surface. With increasing thickness of the coke layer on the exterior of the heater, the temperature tends to build up until it exceeds the melting point of the heating elements causing the latter to fail.

Accordingly, it is an object of my invention to provide a heater capable of withdrawing heat rapidly from a hot bed of oxidation catalyst. It is another object of my invention to provide a heating apparatus by which heat is readily transferred to the exterior of said apparatus through the use of liquid and condensing vapors.

My invention will be more specifically understood by referring to the accompanying drawing in which a well heater 2 comprises an elongated metal case 4 surrounded by a jacket 6. The space between the case and jacket is partially filled with a heat transfer liquid 8. Extending into the catalyst chamber and running the length of the oxidation catalyst bed is tubing 12. The catalyst bed is supported at its base by means of a grate or screen 14, a similar structure 16 is placed at the top of the catalyst bed to minimize entrainment of catalyst with fluids flowing from the heater and on up the well. The heater is attached to well tubing 18 by means of threaded coupling 20.

Patented Dec. 14, 1965 In operation the gaseous or vaporous fuel-air feed mixture passes through tubing 12 the full length of catalyst bed 10 and then flows upwardly through the catalyst where heat is generated by oxidation of the fuel. At the top of the catalyst bed, the resulting products of combustion are conducted up the well and out of the system via the annulus between tubing 12 and tubing 18. The hot catalyst causes heat-transfer liquid 8 to boil. The resulting vapors travel up into the empty space above said liquid and condense, giving up heat to the exterior of the unit. Some heating also occurs by convection of heat through the heat-transfer liquid. Under the conditions described, it is not only possible to fix the maximum temperature at which the heater will operate, i.e., the boiling point of the heat-transfer liquid at the pressure employed, but by the transfer of heat through the jacket wall by means of the hot liquid and condensation of the vapors thereof, it is possible to produce a substantially uniform temperature over a large surface area of the heater in relatively rapid fashion.

The fuel portion of the feed which is to be contacted with the catalyst in accordance with my invention may be selected from a wide variety of substances, such as, for example, light hydrocarbons, typically natural gas, propane, butane and unsaturated derivatives thereof, kerosene, crude oil, oxygenated organic chemicals, such as the lower molecular weight alcohols, for example, methanol, and the like. Mixtures, of course, of two or more of the foregoing materials may be usedin gaseous or liquid formas the fuel component of the feed. In general I prefer to employ air or oxygen-rich fuel mixtures; however, my invention also contemplates the use of fuel-rich mixtures.

Generally speaking, fuel-air mixture volumes or space velocities as high as 100,000 s.c.f.h. (standard cubic feet per hour) per cubic foot of catalyst may be employed. Substantially complete oxidation of the fuel can generally be accomplished at space velocities of this order when suitable fuel-air mixture preheat temperatures are used, such temperatures being determined by means of simple experiment.

The temperature at which the heater operates depends on a number of factors such as, for example, the composition of the feed and the rate of heat generation and heat loss. As the fuel content increases, under an otherwise fixed set of conditions, the generated temperature will be observed to increase. For example, in the case of methanol-air mixtures, the adiabatic temperature rise in the bed is found to increase linearily over a methanol concentration of 1 to 5 mol percent and a temperature range of from 400 to 1500 F.

The catalysts used may be selected from a wide list of materials and form no part of my invention. Typically, catalysts suitable for oxidation of the feeds contemplated herein include the platinum group metals and their oxides. These catalysts are preferably used in very dilute concentrations, e.g., 0.05 to about 0.5 weight percent, and may be supported on materials having a large surface area, such as pumice, aluminum oxide, metal wool, for example, stainless steel wool, and the like. Supported platinum catalyst suitable for this purpose is manufactured by the Chemetron Corporation of Louisville, Ky., and is identified as catalyst G-43. In operation, the portion of catalyst apparently entering into the oxidation reaction is that with which the feed mixture first comes in contact.

The heat-transfer liquid which I employ in utilizing the apparatus of my invention may be selected from a relatively wide range of materials, the preferred one generally being a eutectic mixture of diphenyl and diphenyl ether. This material is commercially available and is generally sold under the trademark Dowtherm. Heavy oils such as the type used in transformers may likewise be employed. One particular advantage, however, of the eutectic mixture mentioned above is that it has a vapor pressure of about 1 atmosphere at 500 F. Thus, when using mixtures of this kind, no high pressures are involved since temperatures substantially higher than 500 F. are generally considered unnecessary for the purpose of reducing the viscosity of heavy oils or for the prevention of excessive paraflin deposition on the formation face and in the Well during production. Actually, the type of heat-transfer liquid suitable for use in my invention forms no part thereof. Such substances may have widely different properties. For example, water may be used in the application of the apparatus of my invention where the jacket is constructed to operate at pressures of the order of about 300 to about 1600 p.s.i.

From the foregoing description, it will be appreciated that the use of a suitable heat-transfer liquid in the manner described herein is not limited to the specific heater design illustrated in the accompanying drawing. On the contrary, the scope of this invention is contemplated to include any catalytic heater in which it is desired to convey the heat generated therein to the exterior thereof in an efiicient and uniform fashion by means of a heattransfer liquid, all as covered by the present claims.

I claim:

1. A bottom-hole heater for oil wells having in combination an elongated cylindrical enclosed vessel, a catalyst chamber therein, a fluid-tight jacket about said vessel defining an enclosed space between said jacket and said vessel, and a conduit extending into said chamber to form an annular space in said chamber and an annular opening at the top thereof, a fuel oxidation catalyst in said chamber, and heat transfer material in said enclosed space to remove heat from said chamber via said jacket.

2. Apparatus for heating an underground formation containing a combustible material and penetrated by a well having a string of tubing therein, said apparatus comprising an elongated cylindrical enclosed vessel adapted to be aflixed to said tubing and having a catalyst chamber therein, a fluid-tight jacket about said vessel defining an enclosed space between said vessel and said jacket, and a conduit within said tubing extending into said chamber to form an annular space in said chamber and an annular opening at the top thereof, a fuel oxidation catalyst in said chamber, and a heat transfer material in said enclosed space to remove heat from said chamber via said jacket.

3. Apparatus for heating an underground formation comprising an elongated cylindrical enclosed vessel having a catalyst chamber therein, a conduit leading into said vessel and into said chamber, a fuel oxidation catalyst in said chamber and surrounding said conduit means for conducting etfiuent from said chamber and a fluidtight jacket about said vessel defining an enclosed space between said vessel and said jacket, and heat transfer material substantially filling said space to remove heat from said chamber to be transferred away from the apparatus via said jacket.

References Cited by the Examiner UNITED STATES PATENTS 1,213,470 1/1917 Finlay 158-99 X 1,637,683 8/1927 Clarkson 165-142 1,812,341 6/1931 Jaeger 23-28892 2,039,603 5/1936 Maier 23-2889 X 2,361,020 10/1944 Gibb 23-28892 2,764,969 10/1956 Weiss 158-96 X 2,839,048 6/1958 Jacklin 126-350 2,902,270 9/1959 Salomonsson et al. 126-360 X 2,972,053 2/ 1961 Anderson 15 8-96 3,107,728 10/1963 Kehn 166-59 FOREIGN PATENTS 708,065 4/1931 France.

FREDERICK L. MATTESON, JR., Primary Examiner.

JAMES W. WESTHAVER, Examiner. 

1. A BOTTOM-HOLE HEATER FOR OIL WELLS HAVING IN COMBINATION AN ELONGATED CYLINDRICAL ENCLOSED VESSEL, A CATALYST CHAMBER THEREIN, A FLUID-TIGHT JACKET ABOUT SAID VESSEL DEFINING AN ENCLOSED SPACE BETWEEN SAID JACKET AND SAID VESSEL, AND A CONDUIT EXTENDING INTO SAID CHAMBER TO FORM AN ANNULAR SPACE IN SAID CHAMBER AND AN ANNULAR OPENING AT THE TOP THEREOF, A FUEL OXIDATION CATALYST IN SAID CHAMBER, AND HEAT TRANSFER MATERIAL IN SAID ENCLOSED SPACE TO REMOVE HEAT FROM SAID CHAMBER VIA SAID JACKET. 